Which cancers are lifestyle related?

Cancer is a deadly disease that affects millions of people worldwide each year. While some cancers seem to occur randomly, many others are closely linked to certain lifestyle factors and exposures. Understanding which cancers may be prevented through lifestyle changes empowers individuals to take control of their health.

What factors influence cancer risk?

Cancer is caused by changes to DNA that allow cells to grow and divide uncontrollably. There are many factors that can cause or contribute to DNA mutations, including:

  • Tobacco use
  • Obesity
  • Physical inactivity
  • Ultraviolet light exposure
  • Ionizing radiation exposure
  • Environmental pollutants
  • Alcohol consumption
  • Poor diet
  • Some viruses and bacteria
  • Family history and genetics

While family history and genetics play a role, it is estimated that over 50% of cancer deaths are linked to preventable causes. This suggests lifestyle factors are major determinants of many cancer risks.

Tobacco-Related Cancers

Tobacco use is associated with at least 12 types of cancer, and accounts for 30% of all cancer deaths in the United States. Tobacco smoke contains over 7,000 chemicals, with at least 70 known to cause cancer.

The most common cancers caused by tobacco use include:

  • Lung cancer – The leading cause of cancer death, responsible for around 154,000 deaths in the US each year. Cigarette smoking causes almost all lung cancers.
  • Oropharyngeal cancers – Cancers of the throat, tongue, soft palate, tonsils and larynx. Risk increases with both smoking and alcohol use.
  • Laryngeal cancer – Cancers of the larynx (voice box). Around 90% are linked to tobacco use.
  • Esophageal cancer – Cancers of the esophagus. Smoking is responsible for 60-80% of esophageal squamous cell carcinomas.
  • Stomach cancer – Increased risk is seen with both smoking cigarettes and exposure to secondhand smoke.
  • Pancreatic cancer – Approximately 20-30% linked to cigarette smoking.
  • Kidney cancer – Around 1 in 5 cases related to smoking. Quitting reduces risk.
  • Bladder cancer – Up to 50% of bladder cancers may be tied to cigarette smoke.
  • Colorectal cancer – Modest increased risk, especially for rectal cancer.
  • Liver cancer – More common in smokers compared to never-smokers.
  • Cervical cancer – Women who smoke are twice as likely to develop cervical cancer.
  • Acute myeloid leukemia – Higher incidence seen among smokers.

Quitting smoking and avoiding secondhand smoke are the most effective ways to reduce risks for these tobacco-related cancers.

Obesity-Related Cancers

Excess body weight is linked to increased risks for 13 cancers, due to hormones, chronic inflammation and other factors. The most common malignancies associated with obesity include:

  • Postmenopausal breast cancer – Being overweight increases estrogen levels, fueling tumor growth. Obese women have a 30-60% higher breast cancer risk.
  • Endometrial cancer – Around 50% are linked to being overweight. Excess fat cells produce estrogen, overstimulating the endometrium.
  • Colorectal cancer – May be up to twice as common in obese individuals. Excess fat may promote tumor growth by releasing inflammatory chemicals.
  • Pancreatic cancer – 20-30% increased risk with obesity, worsened by diabetes complications.
  • Kidney cancer – Higher incidence seen with both obesity and poor blood sugar control.
  • Gallbladder cancer – Overweight women have up to 6 times greater risk compared to healthy weight.
  • Liver cancer – Up to 4-fold increase in risk, worsened by non-alcoholic fatty liver disease.
  • Esophageal cancer – 2-fold higher risk in obese individuals.
  • Gastric cancer – 40% increased risk according to some studies.
  • Ovarian cancer – 20% higher risk with obesity, varies by subtype.
  • Thyroid cancer – May increase risk, especially in women.
  • Multiple myeloma – Higher risk seen in overweight individuals.
  • Meningioma brain tumor – 2-fold increase in risk with obesity.

Losing excess weight, avoiding weight gain, and getting regular physical activity are key strategies to lower risks.

Cancers Linked to Physical Inactivity

In addition to obesity, physical inactivity is an independent risk factor for many cancers. Lack of regular exercise is believed to account for:

  • Up to 25% of breast cancers
  • Up to 27% of endometrial cancers
  • Up to 26% of colon cancers
  • Up to 30% of kidney cancers
  • Around 15% of rectal cancers

Being inactive allows potential cancer-causing hormones and growth factors to accumulate. Exercise helps modulate their levels. Just 30 minutes of moderate activity 5 days weekly is recommended to reduce many cancer risks.

Sun Exposure and Skin Cancers

Ultraviolet (UV) radiation from sunlight and tanning beds is the most preventable cause of skin cancers, which are the most common malignancies diagnosed each year. UV light damages DNA in skin cells, causing genetic mutations that lead to uncontrolled growth.

The 3 main types of skin cancer attributed to sun exposure are:

  • Basal cell carcinoma – Most common skin cancer, rarely spreads. Linked to cumulative lifetime sun exposure.
  • Squamous cell carcinoma – Rarely fatal but more likely to spread than basal cell. Correlated to cumulative sun exposure.
  • Melanoma – Most serious skin cancer. Intermittent, intense UV exposure such as sunburns increase risk.

Staying in the shade, avoiding tanning beds, wearing sun protective clothing and regularly using sunscreen are essential to prevent skin cancer.

Ionizing Radiation and Cancer

Ionizing radiation has enough energy to damage DNA and cause cancer. Examples of ionizing radiation include:

  • UV radiation from the sun
  • X-rays and gamma rays
  • Radon gas (radioactive gas from bedrock)
  • Radioactive fallout from nuclear explosions

Ionizing radiation is a proven carcinogen. Types of cancer clearly linked to ionizing radiation exposure include:

  • Basal cell carcinoma – Most common skin cancer tied to ionizing UV radiation.
  • Bone cancer – Increased rates seen in radium dial painters exposed to radiation.
  • Breast cancer – Small increased risk from medical radiation exposure like x-rays.
  • Leukemia – Increased risk seen in survivors of atomic bombs and nuclear accidents.
  • Lung cancer – Higher rates in uranium miners exposed to elevated radon levels.
  • Thyroid cancer – Elevated in those treated with radiation for other cancers.

While ionizing radiation clearly contributes to cancer risk, exposure from modern medical tests is much lower than in decades past.

Cancers Caused by Infections

Globally, up to 25% of cancers are linked to infectious agents. Some cancers known to be caused by viruses and bacteria include:

  • Cervical cancer – Nearly all cases caused by human papillomavirus (HPV) infection.
  • Hepatocellular carcinoma – Leading cause of liver cancer, linked to hepatitis B, hepatitis C virus.
  • Stomach cancer – Associated with chronic Helicobacter pylori infection.
  • Kaposi sarcoma – Caused by Kaposi sarcoma-associated herpesvirus (KSHV).
  • Non-Hodgkin lymphoma – Increased risk seen with HIV/AIDS and Epstein-Barr virus infection.
  • Urinary bladder cancer – Associated with certain Schistosoma parasitic worms.
  • Merkel cell carcinoma – Rare skin cancer tied to Merkel cell polyomavirus.

Avoiding or treating these infectious diseases through immunization, safe sex practices and modern therapies can help prevent associated cancers.

Alcohol and Cancer Risk

Drinking alcohol increases risks for several common cancers:

  • Oropharyngeal – Cancers of the throat, mouth and voice box. 4-fold increased risk with heavy drinking.
  • Liver cancer – 2 to 3-fold greater risk in those with alcohol abuse disorder.
  • Esophageal cancer – Around 4 drinks daily doubles risk.
  • Breast cancer – Increases breast cancer risk in women by 10% for each daily drink.
  • Colorectal cancer – 1.5 times higher risk in those consuming over 2-3 drinks per day.

For cancer prevention, alcohol intake should be limited to <2 drinks daily for men, <1 for women.

Diet and GI Cancers

Diets high in processed and red meats, low in fruits/vegetables, along with obesity contribute to cancers of the GI tract:

  • Colorectal cancer – Linked to high red/processed meat, alcohol, obesity; reduced by fiber, calcium.
  • Esophageal cancer – Tied to low fruit/vegetable intake.
  • Stomach cancer – Increased risk with high salt, smoked food intake.
  • Pancreatic cancer – Red meat, obesity increase risk.

Eating a diet high in fiber, fruits, vegetables and whole grains may help reduce risks.

Preventable Exposures and Lung Cancer

In addition to smoking, other avoidable lung carcinogens include:

  • Radon – Radioactive gas from soil/rock, accounts for 10% of lung cancers.
  • Asbestos – Workplace exposure causes mesothelioma and lung cancer.
  • Air pollution – Small increased risk, especially with diesel exhaust exposure.
  • Arsenic – Lung cancer risk seen in workers exposed to arsenic.

Avoiding these occupational and environmental exposures, along with not smoking, are key to prevent lung cancer.

Reproductive Factors and Gynecologic Cancers

Reproductive patterns affect hormones and cancer risks:

  • Breast cancer – Increased with hormone therapy after menopause, not breastfeeding.
  • Ovarian cancer – Lower risk with OC pill use, tubal ligation, pregnancies.
  • Endometrial cancer – Increased by early menarche, late menopause.

Understanding how reproductive choices influence cancer risk empowers women to make informed decisions.

Preventing Secondary Cancers

Many cancer treatments unfortunately increase risks for secondary malignancies. However, steps can be taken to minimize risks:

  • Avoiding unnecessary imaging tests that use ionizing radiation.
  • Using sun protection to reduce UV exposure after radiation therapy.
  • Following screening guidelines to detect any new cancers early.
  • Making healthy lifestyle choices to avoid preventable cancers.

Working closely with your care team can help balance curing initial cancer while preventing new cancers.

Genetics and Inherited Cancers

Family history increases risks for 5-10% of cancers due to inherited gene mutations such as:

  • BRCA1/BRCA2 – Breast and ovarian cancer.
  • Lynch syndrome – Colorectal, endometrial, ovarian cancer.
  • CDH1 – Hereditary diffuse gastric cancer.
  • RET – Medullary thyroid carcinoma.

Genetic testing allows early detection and prevention strategies for those at increased genetic risk.

The Bottom Line on Preventable Cancers

While not all cancers are preventable, a significant percentage are closely linked to lifestyle factors and exposures. Some of the most actionable ways to reduce common cancer risks include:

  • Avoiding tobacco use and secondhand smoke.
  • Maintaining a healthy weight and being physically active.
  • Eating a healthy diet rich in vegetables, fruits and whole grains.
  • Practicing sun protection and avoiding tanning beds.
  • Limiting alcohol intake.
  • Getting recommended cancer screening tests.

Making positive lifestyle changes and controlling exposures within your control are impactful ways to reduce your lifetime cancer risk.

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